The use of optical free space communications, i.e. visible light (VL) and infra-red (IR) communications, for the selection and advanced control of light sources has previously been proposed, and will be referred to as coded light (CL). For the transmission of CL, mostly, light emitting diodes (LEDs) are considered as light sources in the luminaires, which allow for a reasonable high modulation bandwidth. This in turn may result in a fast response of the resulting control system. Although LEDs are typically considered, other light sources (incandescent, halogen, fluorescent and high-intensity discharge (HID) lamps) also enable the embedding of identifiers in the light, generally, however, at a lower rate.
CL can be used to embed unique identifiers, or codes, in the light output of different light sources. Using these identifiers the light emanating from a specific light source can be identified in the presence of illumination contributions from other light sources. This identification of the individual illumination contributions allows for applications such as light source selection, point and control, commissioning and interactive scene setting. These applications have use in, for example, homes, offices, shops, cars, and hospitals. These light source identifiers enable a simple and intuitive control operation of a light system, which might otherwise be very complex.
One specific category of applications that CL enables is room-based auto-commissioning. In this application a control device receives modulated light from various luminaires in the room. After extracting the identification codes from the modulated light the control device creates a (wireless) link to the luminaires identified allowing it to control them. This establishing of the binding and the control relation is what hereinafter will be referred to as commissioning.
The sensitivity of the control device forms a practical problem, especially for the luminaires situated remote from the location of the control device. These luminaires only provide a small contribution to the light received by the control device, making it difficult to successfully extract their identifiers. Furthermore, if the individual luminaires emit their identification in a random access fashion (e.g. via the framed ALOHA protocol), many collisions may occur before an identification code is extracted correctly.